1. Field of the Invention
The present invention relates to an IC card in which a pair of panel members are fixed onto the top and bottom surfaces, respectively, of the frame of the card.
2. Description of the Prior Art
Conventionally, for so-called IC cards has been generally and widely employed a structure in which the inner components such as electric circuit boards having specific electronic parts and the like incorporated therein are disposed in a resin frame of which the top and bottom surfaces are covered by a pair of metal panels.
Herein, "IC Card" means a card-like or plate-like apparatus which comprises electric circuits or electronic circuits including semi-conductor circuits, and such cards include cards which are identified by other various names such as PC card, modem card, LAN card, memory card, or electronic card and which have the similar basic arrangement.
There has been known an example of a structure of such an IC card (hereinafter referred to as a prior art 1) in which upper and lower metal panels are joined to a unitary frame body with use of adhesive sheets.
As shown in FIGS. 15-20 as an example of such an IC card according to the prior art 1, an IC card 101 is assembled as follows: A module in which a connector 106 is mounted to one end of an electric circuit board 104 having specific electronic parts and the like 105 incorporated therein is incorporated into a unitary resin frame 102. Adhesive sheets 109 having adhesive applied to both surfaces thereof are temporarily bonded to, for example, the upper and lower surfaces of the frame 102, respectively. Upper and lower metal panels 107, 108 are then integrated with the upper and lower sides of the frame 102 through the medium of the adhesive sheets 109, and are heated under a predetermined temperature condition while being pressed from above and below, so that the metal panels 107, 108 are bonded and fixed to the upper and lower sides of the frame 102.
In the example shown in FIGS. 15-20, the upper and lower metal panels 107 and 108 are provided with bend portions 107b and 108b, respectively, which are formed of edge portions of the panels bent generally by 90 degrees. On the other hand, grooves 102g having a larger width than the thickness of the bend portions 107b, 108b are provided on the upper and lower sides of the frame 102 along edges of the frame 102. When the upper and lower metal panels 107 and 108 are integrated with the upper and lower sides of the frame 102, respectively, the bend portions 107b, 108b are fitted into the grooves 102g on the upper and lower sides of the frame 102.
Also, Japanese Patent Laid-Open Publication HEI 1-146794 (hereinafter referred to as a prior art 2) discloses another example of such a card structure in which the enlargement of the area to be bonded and the reinforcement of the adhesion are achieved by bent portions provided on the circumferences or part of the upper and lower metal panels, and in which the card is assembled by fitting the bent portions into grooves provided on the frame.
Further, Japanese Patent Laid-Open Publication HEI 3-45397 (hereinafter referred to as a prior art 3) discloses such a card structure in which projections are formed on the extremities of bent portions formed on both longitudinal sides of upper and lower metal panels and in which the projections are press-fitted along guide grooves provided on the frame.
Furthermore, Japanese Patent Laid-Open Publication HEI 7-160837 (hereinafter referred to as a prior art 4) discloses such a card structure in which, with use of a case wherein a frame and one panel are integrated, and with a plurality of elastic tongues provided on the other panel, the tongues are fitted into and engaged with grooves provided on the case, by the action of the elasticity of the tongues.
The prior arts mentioned above, however, have their respective drawbacks as follows:
In the prior art 1, the adhesive sheets 109 required to bond and fix the metal panels 107, 108 to the frame 102 cost much particularly because each adhesive sheet 109 has to be shaped like a frame corresponding to the shape of the plan view of the frame 102. Besides, the assemblage of the card requires specialized apparatus and a lot of labor because the obtainment of a required adhesion from the adhesive on the adhesive sheets requires a predetermined temperature (e.g., 150 degrees C) to be maintained and a predetermined pressure (e.g., about 50 kg) to be applied in the assembling process. Additionally, it is generally difficult to achieve a uniform adhesion throughout the peripheries of the metal panels 107, 108 to obtain a stable fixing force, especially because each adhesive sheet 109 is shaped like a frame.
Also, in the prior art 2, the metal panels are fixed to the frame basically by the adhesion, and it is therefore difficult to stably obtain a uniform fixing force along the bent portions, even though the bent portions are provided on most of the peripheries of the metal panels.
Further, in the prior art 3, the extremities of the projections provided on the bent portions of the metal panels are simply press-fitted into the guide grooves on the frame and, as it were, the metal panels and the frame are in point engagement with each other, so that it is difficult to stably obtain a fixing force sufficient to withstand a long-term use. Besides, it is generally difficult to ensure a stable strength, especially because the projections are provided on the extremities of the bent portions.
Furthermore, in the prior art 4, the panels are engaged with the grooves on the case simply by the action of the elasticity of the plurality of tongues, and it is therefore difficult to stably obtain a fixing force sufficient to withstand a long-term use.
For the purpose of avoiding the application of adhesive where possible and fixing the metal panels to the frame basically only with press-fitting force, a method is known in which projections provided on the metal panels are press-fitted into grooves formed on the frame, e.g., as shown in the prior art 3. In this method, it may be possible to obtain a force fixing the panels to the frame, by the press-fit effect of the projections which acts in their longitudinal directions, with a setting in which the width of the grooves is greater than the thickness of the projections by not less than a certain degree so that the projections are made free in the directions of their thicknesses and in which the length of the grooves is smaller than the length of the projections by a given amount. In this arrangement, however, the fixing force acts only at both ends of each projection, thus resulting in point engagement, as it were; it is therefore difficult to stably obtain a fixing force sufficient to withstand a long-term use.
It may also be possible to make such an arrangement as follows: The edge portions of each metal panel are bent generally by 90 degrees over almost all the lengths of the portions to form bent portions (bend portions), and the frame is provided with grooves which have a width smaller than the thickness of the bend portions by a given amount (a slight amount as press-fit margin) and which extend rectilinearly along the frame. The bend portions are press-fitted into the grooves so that a firm fixing force can be obtained by the press-fit effect of the bend portions which acts in the directions of their thicknesses.
The thickness of the metal panels, however, is so small (e.g., on the order of 0.15 mm) that the press-fit margin for producing the press-fit effect in the direction of the thickness of the panels is extremely small. Accordingly, to form rectilinear grooves having the width corresponding to the margin over not less than a certain degree of length requires molding and/or machining with extremely high accuracy and is substantially impossible from the viewpoint of the technology of producing the frame, at least on the premise of not less than a certain degree of mass production.